Field of the Invention
The present invention relates to a power control technique for an image forming apparatus.
Description of the Related Art
In recent years, regulations adopted by various countries have been becoming stricter year after year as measures against environmental issues such as global warming. For example, image forming apparatuses are also no exception, and are required to sincerely address the environmental issues and actively deal with various kinds of energy-related standards.
Further, mobile electronic apparatuses, such as notebook personal computers (PCs) and tablet PCs, are in widespread use. Then, there is Peripheral Component Interconnect (PCI) Express, which is a standard for interfaces of internal buses, for allowing the mobile electronic apparatuses to be kept driven by a battery for a further longer time period. Further, there is Serial Advanced Technology Attachment (SATA), which is a standard for interfaces (IFs) with storage devices.
Power saving states are formulated at a level of a standard. For example, power saving states on an IF between a host and a device are added in SATA. As the former, a Standby command, a Sleep command, and the like are defined. Further, as the latter, Partial, Slumber, and Device-Sleep (hereinafter referred to as DevSleep) are defined as the power saving states. Representative examples of the storage devices include a hard disk drive (hereinafter referred to as an HDD) and a solid state drive (SSD).
The above-described DevSleep state is the power saving state designed especially for the SSD, and enables reductions in both power of the SATA-IF and power of a main body at run-time.
Standby power is a relatively high in the SATA-IF and the storage device connected thereto in an idle state other than a time period when access is ongoing.
Especially, Redundant Arrays of Inexpensive Disk (RAID) control and/or data encryption processing may be performed as an SATA bridge configuration. In this case, high standby power is consumed in central processing unit (CPU) systems of an SATA main control unit that is a host side and an SATA bridge control unit that is a device side, a plurality of storage devices, and a plurality of SATA-IFs (for example, physical layers) connecting them. In this case, runtime power saving control is required.
For example, some HDDs include a Parallel ATA (PATA)-IF. There is an SATA bridge configuration that bridges such an HDD and the SATA host control unit including the SATA-IF. There is a technique for issuing the above-described power saving-related command to the SATA bridge control unit without bothering an upper-level main CPU in this configuration.
More specifically, there is proposed a method for causing the SATA-IF between the SATA host control unit and the SATA bridge control unit, which is the device side, to transition to the above-described Partial or Slumber power saving state according to a status of the power saving control on the HDD (Japanese Patent Application Laid-Open No. 2005-78514).
However, the method discussed in Japanese Patent Application Laid-Open No. 2005-78514 is processing for transitioning the SATA component to a power saving state based on the power saving-related command directed to the HDD. In other words, a power saving state transition condition is not linked with a power state of the entire apparatus, and the transition to the power saving state is determined only based on the SATA component portion alone. As such, there is a limit to finely adjusted power saving control.